1. Field of the Invention
The present invention relates to an air gap anti-siphon system designed for high flow rate drainage of waste water from a household water softener system or the like, but modifiable for low flow rate drainage from a reverse osmosis system.
2. Description of the Prior Art
A typical household water softener continuously treats incoming water by passing it through a resin composition. Water flow through the composition is periodically interrupted so that the resin composition can be flushed with salt water to rejuvenate it. The flow of waste or reject salt water coming out of the resin composition is turbulent and at a relatively high rate. In contrast, the discharge from a typical household reverse osmosis system is at a relatively low rate. At present there is no satisfactory air gap anti-siphon system that is useful for use with a water softener system, and yet which is easily convertible for use with a reverse osmosis system.
Air gap anti-siphon devices of the prior art are generally incapable of blocking sudden sewage backflow, which can occur when either a vacuum or sufficiently low pressure develops in the household lines, or a high pressure develops in the sewer lines, or both. Any sewage backflow into the water softener system or the reverse osmosis system is extremely undesirable because there is then a potential entry point into the potable water system of the household.
The height of air gap specified by most plumbing codes to prevent back siphoning of waste water is usually one inch or more. This is normally adequate to prevent siphoning of relatively slowly rising backflows, but it is not adequate to prevent a high velocity stream of contaminated water from bridging the air gap when a sudden pressure differential develops.
Backflow prevention devices are described in my U.S. Pat. No. 5,176,165. These prevent contamination of household water systems that are associated with the relatively slow flow rate reverse osmosis systems. However, they are not effective in handling the high flow rates associated with a water softener system.
An earlier backflow prevention device effective to handle high flow rates is disclosed in U.S. Pat. No. 3,411,524, entitled "Vacuum Breaker", issued Nov. 19, 1968 to Robert E. Raine and to the present applicant. However, the device is incapable of conversion for use with the low flow rates of reverse osmosis systems. Also, the design makes it almost impossible to install in washing machine outlet boxes of the type now being used.